Laboratory Screening Test for Cotton Seed Germination and Emergence Under Low Temperatures
Apr 18, 2019
Cotton is a tropical perennial plant that is grown in the U.S. as a temperate annual. Approximately 20% of the U.S. crop is produced in the Texas High Plains, an area characterized by a short growing season in terms of accumulated heat units. Cool spring nights can reduce the germination of seeds and establishment of seedlings. The objective of this study was to develop a breeding strategy for accurately, cheaply and quickly screening a large number of genotypes for cold tolerance. Sensitivity to low temperatures occurs during the imbibition phase (imbibition chilling) and again during the germination and emergence phases (metabolic chilling). This test involves rolling the seed in a polyturethane foam pad, wetting with water at 5oC, allowing excess water to drain and then placing in a chamber at 5oC. Seed rolls are removed after 8, 16 and 24 h. Seeds are then placed on the surface of 5cm sand wetted to field capacity and placed in a chamber at 18oC for 21 days. The percentage of emerged seedlings is then determined and corrected by dividing this number by the warm germination test percentage. This allows test results to be based on viable seeds only. In one study, the corrected emergence percentages ranged from 35 to 81 % and in another from 9 to 65% Both these studies had seed subjected to 24 h of imbibition chilling at 5oC. Data from 8 and 16 h of imbibition chilling are reported in addition to imbibition rate data.